On a freezing Indiana night in mid-February, I stepped out of my warm car and hurried into the homeless shelter for my nightly volunteer shift. Seeking respite in the lobby, a young woman, temporarily staying at the shelter, sized me up and whispered, “You’re fly.”

In case you’re unfamiliar with urban slang, it essentially means, “You’re hot.”

Naturally, I was taken aback and somewhat embarrassed by her forwardness, particularly since I wore a wedding ring and had never met her before. How...